The present invention relates to a handheld power tool having a hammer mechanism, preferably a pneumatic hammer mechanism, e.g., a jackhammer. With a beater of the hammer mechanism, the jackhammer strikes a cutter to drive it into a substrate. The momentum of the beater is transferred efficiently to the cutter. However, if the cutter is not in contact with a workpiece, the result is an empty strike. The beater runs into a front stop and transfers the momentum to the handheld power tool. It is known that the front stop may be provided with damping rings made of an elastomer, for example, to absorb the resulting forces and protect the jackhammer.
The handheld power tool according to the invention has a housing, a hammer mechanism and a torque coupling. The hammer mechanism contains a beater, which is movably guided along a working axis. The guide tube is mounted in a suspension attached to the housing so that the guide tube is movable along the working axis. The torque coupling is mounted on the guide tube and supported on the suspension in the impact direction. The guide tube is supported on the torque coupling in the impact direction. The guide tube may be displaced with respect to the housing in the impact direction, such that the torque coupling is shifted by the guide tube in a positively guided movement in relation to the housing.
The momentum transferred to the guide tube in the blank impact is introduced into the housing via the torque coupling. The torque coupling acts as a delay element. The torque coupling expediently has a return spring, which exerts a force on the suspension in the impact direction and exerts a force on the guide tube in the direction opposite the impact direction. The return spring extends the transfer of momentum to the housing and thus also extends the resulting forces.
According to one embodiment, the torque coupling includes, in the direction of impact, a first coupling disk, a second coupling disk and a return spring in this order. The guide tube is supported on the first coupling disk or on the second coupling disk in the impact direction. The return spring acts on the suspension in the impact direction and acts on the second coupling disk in the direction opposite the impact direction. The guide tube can move in the impact direction but only by entraining at least one of the coupling disks. The return spring arranged between the suspension and the coupling disks is compressed in the process. The guide tube may also be engaged between the two coupling disks, thereby raising the first coupling disk from the second coupling disk in restriking. The coupling is thus released briefly in restriking and the transfer of torque is interrupted. Another embodiment extends directly to the return spring to utilize this for damping of the restriking of the blank strike.
One embodiment provides for the suspension to include a first ring rigidly connected to the housing and a second ring extending around the guide tube. The guide tube is axially movable in the second ring, and the second ring is in contact with the first ring in the impact direction. The return spring may be in contact with the second ring.
The following description illustrates the invention on the basis of exemplary embodiments and the FIGURE.